This report presents the process of developing an experimental test setup of a laboratory-scale convective industrial heat pump dryer. The setup is designed to test various zeotropic mixtures as refrigerant. Previous research has shown that the use of zeotropic mixtures as refrigerant in a heat pump dryer can increase the efficiency. This is used as the foundation for the present study, as it provides optimized cycles for various zeotropic mixtures.

A literature study is performed on dryers and heat pump technology, to form a foundation for further research in the field of industrial heat pump dryers. Regarding dryers, various drying techniques as well as the underlying psychrometric principles were reviewed to establish a clear understanding of moisture removal processes and their relevance to convective heat pump dryers. Additionally, the review of heat pump technology covered both the overall heat pump cycle and each of its individual components. For the heat exchangers and compressors, different types were examined, along with an assessment of which options are most suitable under specific operating conditions. In addition, various developments related to refrigerants were examined. This is followed by the collection of design requirements based on the cycles from the earlier study. Subsequently, a test setup is designed in which the refrigerant mixtures 87.5%_mol CO₂-Isopentane and 90%_mol  CO₂-Isobutane can be evaluated. 

The design process begins with the selection of a compressor, based on the design requirements and the laboratory constraints. A reciprocating compressor was chosen. The cycle is then recalculated using the updated compressor specifications. Next, the heat exchangers are designed. A model is used to determine the required surface areas, heat transfer coefficients, and pressure drops of finned tube heat exchangers. Based on these results, final designs are established for both the gas cooler and evaporator. The dryer is then designed as the final major component. A nozzle is selected and the droplet evaporation time is calculated. 

Once all main components are designed and selected, a sensitivity analysis is performed to evaluate how the system responds to variations in several key parameters. This includes changes in the inlet air conditions, the outlet conditions of the dryer, the effect of air velocity on the system performance and the impact of changing the refrigerant mixture. Finally, all components are integrated into the final design. Additional essential elements are included, and specific attention is given to safety, instrumentation, and the refrigerant replacement procedure. 

The results of this research can contribute to validating the potential efficiency improvements of heat pump dryers when using zeotropic mixtures as refrigerants.